How to Get Rid of White Alkaline on Cinder Block Walls

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The chalky white substance so often found on old brick, cement or cinder block walls is efflorescence. It's an alkaline substance composed of salts and minerals from the concrete itself in addition to those in the ground surrounding your home. Masonry is by nature porous, so any moisture travels through, carrying these salts and minerals to the surface. There, it dries, leaving a white powder residue. It not only looks bad, but it can damage existing finishes and hinder the application of new ones. Simply sealed over, the trapped efflorescence, now transformed to crytoflorescence, expands until it shatters the masonry. Cleaning up the efflorescence is, fortunately, a simple process.

1

Squirt a few drops of liquid dish soap into a 5-gallon bucket and fill with warm water. Dip a stiff-bristled brush or a plastic scouring brush into the soapy water and scrub the wall. Rinse the brush constantly while working across and down the wall surface.

2

Rinse out the bucket and flush the soapy water from the brush. Refill the bucket with fresh, warm water, if the wall is inside, and scrub the wall again with plain water to rinse the soap from the masonry. Follow with a wet sponge or cloth to ensure all residue and debris is removed. Use a garden hose and sprayer, if the wall is outside.

3

Dry the walls with fans, pointed at the wall and blowing to speed evaporation, if working on the inside of the house. Allow the wind and sun to dry surfaces outside. Scrub the wall with a dry brush as it dries if a faint amount of efflorescence lingers. Proceed with a stronger cleaning solution if large amounts of efflorescence remain.

4

Wet the wall, using a bucket of water and cloth or sponge inside or a hose and sprayer outside. Soaking the wall before using strong chemicals prevents the masonry from absorbing too much, which can deteriorate the ingredients inside the concrete and lead to wall failure.

5

Mix a solution of half vinegar and half water or add a few drops of trisodium phosphate to a bucket of warm water. Vinegar provides an environmentally friendly approach, and either can be used indoors or outside. TSP works particularly well on surfaces with mold and mildew. Vinegar is slightly stronger, however. As an acid, it naturally neutralizes the alkaline properties in the efflorescence.

6

Scrub the wall with the vinegar or TSP mixture. Dip the brush in the cleaner frequently to rinse and apply fresh solution. Also rub across the wall with a cloth or sponge saturated with the solution. Allow the wall to sit, wet, for five to 10 minutes minimum. This allows the vinegar or TSP time to work.

7

Rinse off the wall with fresh, clean water. Use a hose and sprayer outside, or fill a bucket with warm water and wipe over the wall with a sponge or cloth. Change the water occasionally and cover each area at least twice to ensure the wall is completely flushed. Any lingering TSP or vinegar can degrade the concrete over time.

8

Seal the wall with a masonry sealer once the wall is completely dry -- at least two or three days. Follow the product instructions for application. The sealer helps prevent future efflorescence and other problems.

Things You Will Need

Liquid dish soap

5-gallon bucket

Stiff-bristled brush

Sponge

Cloths

Garden hose with sprayer

Vinegar

Trisodium phosphate

Masonry sealer

Tips

Eliminate any source of moisture to the walls that can be prevented. Repair cracks and holes in the masonry before cleaning. Ensure water drains away from the wall. Proper ground slope, house overhangs, eaves troughs and other methods of draining water help keep efflorescence from returning.

Sandblasting and muriatic acid are popular alternatives to vinegar and TSP. However, sandblasting is structurally damaging to the concrete and leaves it more porous than before. Muriatic acid, mixed 1 part to 12 parts water, works well. However, muriatic acid is hydrochloride -- a dangerous chemical. It produces strong fumes and can burn your skin instantly. Never use without plenty of ventilation and protective wear such as long sleeves and a respirator. In addition, do not pour the acid into water -- pour water into the acid instead -- to prevent backsplash. Use only plastic or glass tools with muriatic acid as it reacts chemically with metal.

About the Author

Karie Fay earned a Bachelor of Science in psychology with a minor in law from the University of Arkansas at Monticello. After growing up in construction and with more than 30 years in the field, she believes a girl can swing a hammer with the best of them. She enjoys "green" or innovative solutions and unusual construction.